Except the advantages of light weight and thin, flexible and low-glare, the organic light-emitting diode (OLED) further has special performances of high color rendering and full spectrum. It quite fits the requirements of current illumination products, such that OLED becomes a focal point of the next generation illumination technology.
In recent years, the efficiency and life span of the R, G, B light emitting materials of the OLED have significantly improved. The efficiency of the green phosphorescent material has been over 1001 m/M, and the life span thereof also has been the top among various colors of illumination materials, which can sustain hundreds of thousands of hours. However, the most critical blue light emitting material in the white light OLED element relatively falls behind.
Although the current efficiency of the blue phosphorescent material has achieved 20.4 cd/A, its life span is merely hundreds of hours. Recently, most of the literature use the phosphorescent material “bis(4,6-difluorophenylpyridinato-N,C2) picolinatoiridium(FIrpic)” as major blue phosphorescent material. The efficiency of FIrpic is high, but the life span of it is not satisfactory. Therefore, the all-phosphorescent white light OLED element is highly efficient though it is not able to be applied in the illumination because of the short life span. In addition, the blue fluorescence material has worse efficiency, which is only 10.2 cd/A, but its life can achieve thirty thousand hours. Thus, the blue fluorescence material is temporarily accepted by the industry. It is generally called hybrid white light OLED element.
For this reason, how to develop a high efficient white light OLED element without using blue light emitting materials (the blue phosphorescent material or the blue fluorescence material) becomes a key issue of the current market.